Glomerulonephritis in Horses: Protein Loss and Kidney Damage

Quick Answer
  • Glomerulonephritis is inflammation and damage in the kidney's filtering units, called glomeruli, which can let protein leak into the urine.
  • Common clues include ventral or leg swelling, weight or muscle loss, low blood protein, and proteinuria found on urinalysis.
  • Some cases are linked to immune-mediated disease, chronic inflammation, infection, amyloidosis, or high blood pressure, but the trigger is not always found.
  • Diagnosis usually starts with urinalysis, urine protein measurement, bloodwork, blood pressure, and ultrasound. Some horses need a kidney biopsy to confirm the cause.
  • Treatment focuses on the underlying problem, careful fluid and diet planning, and monitoring for kidney failure, edema, and progression to chronic kidney disease.
Estimated cost: $350–$3,500

What Is Glomerulonephritis in Horses?

Glomerulonephritis is a disease of the glomeruli, the tiny filters inside the kidneys that help clean the blood while keeping important proteins in circulation. When these filters become inflamed or damaged, protein can leak into the urine instead of staying in the bloodstream. Over time, that protein loss can contribute to low blood protein, fluid buildup, muscle loss, and worsening kidney function.

In horses, glomerular disease is considered uncommon, but it can be serious. Merck notes that glomerular disease in horses often leads to protein in the urine, low blood protein, fluid accumulation in the abdomen, shortness of breath, and swelling in the legs, and many affected horses eventually develop chronic kidney disease or kidney failure. Because early kidney disease can be subtle, some horses are first identified when routine lab work shows proteinuria.

Glomerulonephritis is not one single disease pattern. In some horses it appears to be immune-mediated, meaning immune complexes or immune injury damage the kidney filters. In others, the glomeruli are affected by related problems such as amyloidosis, systemic inflammation, or long-standing disease elsewhere in the body. That is why your vet usually looks beyond the kidneys and evaluates the whole horse.

Symptoms of Glomerulonephritis in Horses

  • Ventral edema or swelling under the belly
  • Swelling of the legs or lower limbs
  • Weight loss or loss of topline and muscle mass
  • Poor performance, lethargy, or reduced stamina
  • Increased drinking and urination
  • Protein in the urine found on testing
  • Low blood protein or albumin on bloodwork
  • Abdominal fluid buildup or a pot-bellied appearance
  • Shortness of breath or increased respiratory effort from fluid accumulation
  • Signs of kidney failure such as depression, poor appetite, or worsening dehydration

Some horses with early glomerular disease have very few outward signs. Others develop a more obvious protein-losing kidney pattern, with edema, weight loss, and low albumin. If your horse has new swelling under the belly or in the legs, unexplained weight loss, or lab work showing proteinuria, schedule a veterinary visit promptly.

See your vet immediately if your horse has trouble breathing, marked abdominal distension, severe lethargy, poor appetite, or signs of worsening kidney function. Those changes can mean the disease is progressing or that fluid balance is becoming unstable.

What Causes Glomerulonephritis in Horses?

In horses, glomerulonephritis is often thought to be immune-mediated. That means the immune system forms complexes or triggers inflammation that damages the glomeruli. Merck also lists amyloidosis and high blood pressure among conditions that can affect the glomeruli. In practical terms, your vet may look for chronic inflammatory, infectious, or systemic disease that could be driving ongoing immune stimulation.

Sometimes glomerular injury develops alongside broader kidney disease rather than as an isolated problem. Horses with severe systemic illness, chronic inflammation, or long-standing renal injury may show proteinuria as part of a bigger picture. In some cases, no clear trigger is identified even after a thorough workup.

It is also important to separate glomerulonephritis from other kidney problems that can look similar at first. Horses can develop kidney injury from dehydration, sepsis, reduced blood flow to the kidneys, anesthesia-related complications, or nephrotoxic drugs such as aminoglycosides and NSAIDs. Those problems more often affect the renal tubules, but they can overlap clinically with glomerular disease and may change how your vet approaches treatment and prognosis.

How Is Glomerulonephritis in Horses Diagnosed?

Diagnosis usually starts with a careful history, physical exam, and urinalysis. Protein in the urine is one of the most important clues. Your vet will often pair that with bloodwork to look for low total protein or albumin, cholesterol changes, dehydration, and evidence of reduced kidney function. Blood pressure measurement can also help, because hypertension can both contribute to and result from kidney disease.

Imaging is commonly part of the workup. Ultrasound can help assess kidney size, shape, and other structural changes, while additional tests may be used to rule out stones, infection, or other urinary tract disease. If infection is a concern, urine culture may be recommended.

A kidney biopsy is sometimes needed to confirm the type of glomerular disease and to distinguish glomerulonephritis from other causes of protein loss, including amyloidosis. Merck specifically notes that biopsy is often required to determine the cause of glomerular disease in horses. Because biopsy carries cost and procedural risk, your vet will weigh whether the result is likely to change treatment decisions.

In many horses, diagnosis is really a combination of two goals: confirming that the kidneys are losing protein, and identifying the underlying disease process that may be driving that loss. That broader search may include infectious disease testing, inflammatory screening, and repeat monitoring over time.

Treatment Options for Glomerulonephritis in Horses

Spectrum of Care means you have options. Here are treatment tiers at different price points.

Budget-Conscious Care

$350–$900
Best for: Stable horses with mild proteinuria, mild edema, or early suspected kidney disease when the pet parent needs a stepwise plan.
  • Farm call or outpatient exam
  • Basic bloodwork and urinalysis
  • Focused assessment of hydration, edema, and body condition
  • Review of current medications and removal of possible nephrotoxic drugs when appropriate
  • Supportive plan for water access, forage-based nutrition, and monitoring appetite, manure, urination, and swelling
  • Short-term recheck labs if the horse is stable
Expected outcome: Variable. Some horses remain stable for a period with monitoring and management of underlying disease, while others progress and need more diagnostics.
Consider: Lower upfront cost, but the exact cause may remain unclear. Without imaging, blood pressure, or biopsy, it can be harder to predict progression or tailor therapy.
Most Common

Recommended Standard Treatment

$900–$2,200
Best for: Most horses with confirmed or strongly suspected glomerular disease, especially those with edema, low protein, or declining kidney values.
  • Comprehensive exam and serial monitoring
  • CBC, chemistry panel, albumin/total protein assessment, and urinalysis
  • Urine protein quantification when available
  • Blood pressure measurement
  • Renal ultrasound
  • Targeted testing for infectious or inflammatory triggers based on exam findings
  • Individualized fluid planning if needed, with caution in horses with edema
  • Diet and medication review, plus treatment of the underlying condition when identified
Expected outcome: Guarded to fair, depending on the cause, severity of protein loss, and whether chronic kidney disease is already present.
Consider: Provides a more complete picture and often improves decision-making, but still may not give a definitive tissue diagnosis.

Advanced / Critical Care

$2,200–$6,000
Best for: Horses with severe protein loss, marked edema, respiratory compromise, suspected nephrotic syndrome, or progressive kidney dysfunction.
  • Referral hospital care or hospitalization
  • Frequent bloodwork, urinalysis, and fluid-balance monitoring
  • Advanced imaging and specialist consultation
  • Kidney biopsy when indicated to distinguish glomerulonephritis from amyloidosis or other glomerular disorders
  • Management of severe edema, nephrotic syndrome, hypertension, or kidney failure complications
  • More intensive treatment of the underlying immune-mediated, infectious, or systemic disease
Expected outcome: Guarded. Some horses can be stabilized, but advanced disease carries a meaningful risk of chronic kidney failure and long-term management needs.
Consider: Most information and monitoring, but highest cost range and not every horse is a good candidate for invasive testing or hospitalization.

Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.

Questions to Ask Your Vet About Glomerulonephritis in Horses

Bring these questions to your vet appointment to get the most out of your visit.

  1. Do my horse's lab results suggest glomerular protein loss, or could another kidney problem be causing the proteinuria?
  2. How low are my horse's albumin and total protein levels, and are they enough to explain the swelling I am seeing?
  3. What underlying diseases do you think we should look for, such as chronic inflammation, infection, amyloidosis, or high blood pressure?
  4. Which tests are most useful next in my horse's case: repeat urinalysis, urine protein measurement, ultrasound, blood pressure, or biopsy?
  5. Is my horse stable enough for outpatient care, or do you recommend hospitalization?
  6. Are any current medications or supplements adding kidney stress or changing fluid balance?
  7. What feeding and hydration plan makes sense for my horse right now?
  8. What signs at home would mean the disease is worsening and I should call right away?

How to Prevent Glomerulonephritis in Horses

There is no guaranteed way to prevent glomerulonephritis, because some cases are tied to immune dysfunction or diseases that are not obvious early on. Still, the best prevention strategy is to reduce avoidable kidney stress and address chronic disease promptly. That means keeping up with routine exams, investigating unexplained weight loss or edema early, and following through on recommended testing when bloodwork or urinalysis is abnormal.

Good hydration matters. Horses with dehydration, severe illness, or reduced blood flow to the kidneys are at higher risk for kidney injury overall. Careful use of potentially nephrotoxic medications is also important. Aminoglycosides and NSAIDs can contribute to kidney damage in some horses, especially when dehydration or other risk factors are present, so these drugs should only be used under your vet's guidance.

If your horse has a chronic inflammatory or infectious condition, managing that problem well may lower the chance of ongoing immune stimulation that could affect the kidneys. For horses already known to have proteinuria or kidney disease, prevention shifts toward monitoring: repeat urinalysis, bloodwork, blood pressure checks when indicated, and early response to swelling, appetite changes, or increased drinking and urination.

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